Age-hardenable austenitic iron base high temperature alloys



1366- 1964 N. R- HARPSTER AGE-HARDENABLE AUSTENITIO IRON BASE HIGH TEMPERATURE ALLOYS 2 Sheets-Sheet 2 Filed March 6, 1963 O X 2 u m m a. l G G r o m A aw N N N 3 .m E E E 0 N6 m A R R .H R -G 0 T T 2 A -N s s 0 2 .m F o 5 D. C? 0 -.L c. l E D M n E A T L 0 0 i N A E c $7 5 I. Y E O. .l H 0 II T 0 s 2. C 6 ll 0/ .L 0 A 2 8 U l U B M m D m 0 7 R E- F u n o 0 .I .m o 0 d o 0' O I 5 0' B II n C3 5 c V A n x w In I l r H H 0 i Q 0 I Q Q m 2 O O N X m l m 0 h c o F r o C 0 0 0 O O O O O 2 8 6 4 w B m M Q m Q0 09.4 3 5:231

19.2 Norman R.Harpsfer Y B M/M United States Patent Ofitice 3,163,526 Patented Dec. 29, 1964 AGE-HARDENABLE AUSTENITIC IRON BASE HIGH TEMPERATURE ALLOYS Norman R. Harpster, Canonsburg, Pa., assignor to Universal-Cyclops Steel Corporation, Bridgeville, Pa., a corporation of Pennsylvania Filed Mar. 6, 1963, Ser. No. 263,312

8 Claims. (Cl. 75-128) The present invention relates to austenitic iron base alloys which can be hardened by solution and aging treatments and which are substantially non-magnetic and possess relatively high room temperature properties in combination with satisfactory strength characteristics at elevated temperatures.

This application isa continuation-in-part of application Serial No. 827,157, filed July 15, 1959.

Materials for high temperature applications quite frequently must possess relatively high room temperature properties in combination with good strength properties at elevated temperatures. Several of the so-called super alloys have this desired combination of properties but are relatively expensive. The commonly available austenitic stainless steels posses-s satisfactory high temperature properties for many applications, but have strength properties at room temperature appreciably below those desired. For some applications, the ordinary austenitic stainless grades have been successfully used by employing cold or hot-cold Work to increase room temperature strength. While this method of increasing room temperature properties is satisfactory for some applications, it has many limitations; for example, where forging or welding is employed in fabrication. In such cases, it is not possible to use material initially received in such condition and, therefore, it has been customary to use,

for such applications, the more expensive super alloys which can be hardened by heat treatment. A definite need exists for an inexpensive age-hardening austenitic alloy having a combination of good room temperature and elevated temperature properties.

In many applications where both good room temperature and elevated temperature properties are necessary,

it is also necessary that the alloy be substantially nonmagnetic. This is particularly important in critical magnetic and electrical equipment which should not be magnetically affected by the materials used in nearby structures or tools. 7 A specific application of this type is retainer rings used for supporting large motors. A number of non-magnetic non-ferrous metals super alloys and stainless steels-are available for such applications, but the strength and other mechanical properties of such materials are frequently inadequate or fabrication is difficult, or the alloys are too expensive for consideration.

I have found that the desirable attributes indicated above, namely, a'ge-hardenability, high room temperature physical properties, high strength at elevated temperatures, and low permeability, can be obtained in a carbonmanganese-chromium-nickel-vanadium steel by maintaining the various elements. mentioned within certain relatively narrow ranges.- I have also found that the alloys which I provide remain substantially non-magnetic irrespective of the amount of cold work to which they are subjected and that cold working does not materially modify the age-hardening characteristics. In addition to I I any great difficulty.

FIGURE 1 is a graphical representation of the effect of carbon on the tensile properties of an austenitic iron base alloy in the solution treated and aged condition at room temperature; and

FIGURE 2 is a graphical representation of the effect of vanadium on the tensile properties of an austenitic iron base alloy in the solution treated and aged condition at room temperature.

The alloys of my invention possessing the properties indicated above fall within the following composition ranges:

Percent 0.35-0.60 8.0-12.0 1.0 max. 6.0-10.0

Carbon Manganese Silicon Chromium Nickel u 4.0-8.0 Vanadium 1.1-1.8 Sulphur .03 max. Phosphorus .05 max.

Iron Balance In the alloys of my invention, the austenitic structure is provided by the manganese and nickel and the two, therefore, should be used in such amounts as to assure an austenitic structure, but they also should be maintained within approximately the limits stated above in order to provide adequate non-magnetic properties. When manganese, nickel and other elements mentioned above are maintained within approximately the limits stated, the maximum permeability of the alloys will be approximately 1.2 or less when tested at either 100 or 200 oersteds and will retain their low permeability when subjected to cold working. Vanadium, of course, has an effect on ductility at elevated temperatures and on oxidation resistance and it is, therefore, necessary that the vanadium be kept sufficiently low to avoid either of these adverse effects. Chromium, ofcourse, has a desirable effect on corrosion and oxidation resistance. Therefore, the chromium content should be maintained within the ranges specified in order to achieve adequate corrosion or oxidation resistance and, at the same time, to accomplish the desired precipitation hardening.

While I have specified that the carbon content should be between 0.35 and 0.60% and have not specified the presence of nitrogen, some nitrogen may be present and may be deliberately added during manufacture in order to partially replace or augment the carbon Without any material deleterious effect upon the desired properties.

While the broader composition ranges specified above will provide alloys having the above-mentioned properties,

a preferred composition range is as follows:

- Nickel 7.0-8.0

I Carbon Vanadium Vanadium 1.35-1.65 Sulphur .03 max.

Phosphorus a; .05 max.

Iron Balance Atypical alloy embodying my invention is as" follows,

Percent 0.53 Manganese 9.0

Silicon 0.50

Chromium 7.50 Nickel 7.50 p 1.50 Sulphur .01 Phosphorus i .035

Iron Balance Samples of alloys embodying my inevntion were also subjected to similar solution treatments and age-hardened at various temperatures and the tensile properties determined. The various treatments and the tensile properties 5 obtained are set forth beiow'in Table II.

Table II 0.02%"Yield 0.2%Yield Ultimate- "Elong., 12720. 0: Aging Treatment Strength, Strength, Strength, percent Area,

p.s.i. 'p:S.i. pZs.i. i percent SolutionTr'eatnient: '2,000 F., 1 Hour, Water:

1,300- F., 4 Hours, 'Air 69, 500' 88,000 145, 000 '33.3 51. 1 Solution Treatment: 2,050 F., 1 Hour, Water:

1,300" 'F.,' 4Hoi1rs,Air 96,500 115, 500 '160, 000 '25. 0' 5017 Solution Treatment: 2,100'F.,'1 Hour,Water:

1,300 F., 4 Hours, Air 139,000 165, 000 190, 500 9.1. 18. 8 Solution Treatment: 2,150 F.,' 1 Hour, Water:

None .53, 000 59,500 124, 500 Y 62. 7 "70.7 1,100 E, 16 Hours, Air 123,500 139,000 163, 500 18. 3 24. 3 '1,200 F.,'4"H01'11S,A'ir. 115,500 127,500 159,500 30. 7 3357 1,200 F., 16 Hours, Air 128, 600 157,500 176,500 11; 4 162 1 1,300 F., 4 Hours, Air. 147, 000 174, 500 109, 000 6.9 12.3 1,300 F., 16 Hours, Air 140, 000 168, 000 196, 500 '7. 7 11.14 1,400 F., 4 Hours, Air. 127, 500 .154, 500 189,000 9.3 16.0 1,4 'F., 16 'Hours,Air 111, 500 139, 000 178, 500 12. 7 21.1

ability of 1.008 when tested at 50 oerstedsand' 1.009 when tested at'100 oersteds and at'200 oersteds. The alloy tested had been solution-treated at 215 0F. for one hour, Water-quenched, aged for 16 hours at 1300 "F. and aircooled. Another alloy embodying. my invention showed a permeability of 1.001 when tested at100 oersteds and also when testedat 200 oersteds. This alloy had been subjected to thesame 'heat treatmentas'that just stated. The magnetic characteristics of this alloy were also determined after it had been subjected to cold reductions In addition to the above-mentioned'tests, theieifects of cold reduction on the alloys of my invention were determined. Hot rolled plates werefirst'solution'treated for one hour at '2150" F. and water-quenched. Some of the samples were subjected to cold reduction, the reductions .being 20%, and%. :Some of the-samples were thenaged-by' heating for various times at various temperatures and air-quenched. The Rockweli-C hardness values determinedfor'these-samples are set forth '11: of 10%, 20%, 30% and 40% and 1t was-found that -at Table In each stage of the reduction, thealloyhad a -permeability of less than 1.002 when tested at 100 oersteds' and also bl 111 when tested at 200 oersteds. This indicates that the composltion is quite stable in regard to magnetic character1s- Rockwell C Hardness tics.

In order to determine the response to age-hardening Aging Treatment Cold Reduction, of a hotrolledplates embodying my invention, samples were-solution treated for one hour at 2000 11,2100"; F., None 95 2150" F. and 2200'Frand'water-quenchedand then agehardened at various temperatures for 16 hours and then NO1e 23,5 31.5, v41.0 43:5 air-quenched. 'The'Rockwell'Chardnessvaluesobtained ::f %gf' a 1000F 4Hours 27.0 -35.5 43.0 4610 are Set forth below m Table I 1000 F.:'16.Hour's, 29.5 36.0 45.5 47.5 estates: as as o s 0.0 7 Table I so 11200 1 14300 Air. 37.5 43.5 40.0 48.0 %.,'i61;1ours,A1r g gag 27.2 48:5

';0u.rs -5. 0. 46.0 R k ucyfi -dness 1,3(0F.:'l6Hours,A1r 15.0 45.5 4415 43.0 1,4009)? ,4H0urs,A1r. 12.0 43.0 42.0 39.0 e e ,gg8: ,16 0ms 1r 43.0 39.0 35.0 1;! ours 8. 40.0 38.0 35.0 Heat Treatment V Solution Treatmen PH gk 291.5 g Y ours 1r I "29:0 MOOOR 2,100 R 21500 E 2,2000 R 1:600F I 16Hours,A1r 32.0 315 275 25.0

325 3: 5 H ot rolled'fia ts (I X%") weresolutiontreatedforlhoure122150F.

38:5 & 4L5 andw'ater'quenched prior til-indicated percent cold reduction. 1,300 E, 16 Hours, Air M305, 41,5 4 3,5 44,5 1,400 F., 16 Hours, Air- 33.5 40. 0 43.5 43.0 1,500 F., lfi-gours Airu g V 1.600 F. 16 ours,Air Y u V. No Heat'Trea'tn'Jent 97 90 93 V 02 Some of such samples were tested to determine the tensile properties. The treatments to which the material All samples 'were treated for 1"ho'1ir'at indicated temperature and water quenched.

9 B scale.

belowin Table IV.

Table IV 0.02% Yield 0.2% Yield Ultimate Elong, Bed. of Aging Treatment Strength, Strength, Strength, percent Area,

p.s.1. p.s.i. p.s.i. percent Condition: Solution Treated (2,150" F., 1

Hour, Water):

None 53, 000 59. 500 24, 500 62.7 70. 7 1,200 E, 16 Hours, Air 128, 500 157, 500 176, 500 11. 4 15.1 Condition: Solution Treated Plus Cold Reduced I None 77, 000 93, 000 135, 500 50. 8 65. 0 1,200 F., 16 Hours, Air 145, 500 169, 500 192, 500 10. 8 16. 7 Condition: Solution Treated Plus Cold Reduced one 96,500 123,000 150,000 31. 8 61. 3 1,200 F., 16 Hours, Air 144, 500 178, 500 201,000 4. 3 8. 4 Condition: Solution Treated Plus Cold Reduced None 1 08, 500 149, 500 170,000 19. 8 54. 0 1,200 F., 16 Hours, A111--- 159,000 188, 500 210, 500 1. 9 7.4 Condition: Solution Treated duced 7 None 120, 500 166, 500 194, 000 14. 5 49. 4 1,200 F., 16 Hours, Air 138, 500 188,900 218,000 2. 5 5. 6

Forged rings approximately 14%" CD. by 12%" ID. were made and subjected to solution and aging treatments and the tensile properties of transverse specimens thereof determined. The treatments and tensile properties I ment and aging prior to testing. As illustrated, an alloy having less than about 0.35% carbon has relatively poor strength properties and relatively high ductility while an alloy having more than about 0.60% carbon exhibits a are set forth below in Table V. 25 relatively small increase in strength with a substantial de- T able V 0.02% Yield 0.2% Yield Ultimate Elong, Bed. of Aging Treatment Strength, Strength, Strength, percent Area, psi. p.s.i. p.s.i. percent Solution Treatment: 2,050 E, Hour, Water:

1,200 F., 4 Hours, Air 89, 500 103, 500 146,500 39. 6 41.8 1,300 F., 4 Hours, Air 117, 500 141,000 172, 500 18.0 32.2 Solution Treatment: 2,100 F., Hour, Water:

1,200 F., 4 Hours, Air 110,000 123, 500 160, 000 27. 7 28. 8 1,300 F., 4 Hours, Air 116, 500 151, 500 '186, 000 14. 2 25.0 Solution Treatment: 2,150 F., Hour, Water:

1,200 F., 4 Hours, Air 116, 500 134,000 163,000 21.1 23. 6 1,300 F., 4 Hours, Air 127,000 160,000 191, 500 10. 4 16.3

values set forth below in Table VI. The alloy tested was in the form of hot rolled flats previously subjected to heat treatment at 2100 F. for /2 hour, water quenched, aged at 1300 F. for 4 hours and then air quenched.

Table VI Test 0.2% Yield Ultimate Elongation Reduction Temperature Strength Strength (percent) of Area F.) (p.s.i.) (p.s.i.) (percent) It will be seen from Tablesl to V1, inclusive, and the information set forth above in regard to magnetic properties that alloys embodying my invention possess the desirable properties mentioned heretofore and it also will be apparent that such alloys can be inexpensively.

--Tli'e' superior tensile properties of an alloy having my composition as'compared to those of other alloys having the same elements in amounts outside the critical ranges in the alloy of my invention is particularly illustrated by FIGURES 1 and 2. FIGURE 1 shows the results obtained from tests carried out at room temperature on an an alloy having the manganese silicon, chromium, nickel and vanadium within-the respective ranges of my composition and in which the amount of carbon was varied from below 0.35% to above 0.60%, the minimum and maximum, respectively, for the alloy of my invention. Each of the alloys was subjected to the same solution treatcrease in ductility as the amount of carbon increases. It

is apparent from the curves shown in FIGURE 1 that an allioy having 0.350.60% carbon has both good strength produced relatively and good ductility; Whereas less than 0.35% carbon causes a significant decrease in strength and more than 0.60% carbon results in a decrease in ductility without an appreciable increase in strength.

FlGURE 2 shows the results obtained from tests carried out at room temperature on an alloy having the carbon, manganese, silicon, chromium and nickel within the respective ranges of my alloy and in which the amount of vanadium was varied from below 1.1% to above 1.8%, the respective minimum and maximum for the alloy of my invention. Prior to testing, each of the alloys was solution treated. and aged in the samemanner. The curves of FIGURE 2 show that an alloy having less than about 1.1% vanadium has relatively poor strength char acteristics and that the decrease in'ductility is relatively small between 1.1 and 1.8% vanadium. lfmore' than about 1.8% vanadium is added to the alloy no increase in either ductility or strength is obtained and, hence, more than 1.8% vanadium merely increases the cost of the alloy without any increase in the physical properties thereof. As shown by FIGURE 2, an alloy having 1.1- 1.8% vanadium exhibits significantly higher strength properties than an alloy with less than 1.1 vanadium.

Additional tests have been made to determine the effects of several chemistry variations on the tensile properties of my alloy. The different'chemistry variations of the five heats which were melted are shown in Table VII.

7 5 Table VII elevated temperatures, low magnetic permeability, good hot and cold working characteristics and good age-hard- Heat Alloying Element, Percent enability. Number 4. An alloy as claimed in claim 3 having a perme- Mn s1 Or Ni V Fe ability not greater than about 1.2.

,648 mg 7.62 HA0 L09 Balance 5. An austenitic iron base alloy consisting essentially 6.25 0.31 4.02 11.52 a. 65 D0. of carbon about 0.53%, manganese about 9.0%, s1l1con 3: 3 8:33 $153 2:32 58: about 0.5%, chromium about 7.5%, nickel about 7.5%, 11.57 0.59 10.00 7.52 1.72 D0. vanadium about 1.5%, sulphur about .01%', phosphorus 5 10 about 035%, and the balance substantially all iron and In order to test the tensile properties and hardness of incidental impurities, said alloy being characterized by the product or each heat four blanks were obtained from good physical properties at both room temperature and each heat which were solution treated at 2100 F. for elevated temperatures, low magnetic permeability, good /2 hour, water quenched, age-hardened at 1300 F. for hot and cold working characteristics and good age-hard- 4 hours and air cooled. After heat treatment, the blanks enability.

Were mac ined to a tensile specimen having a gauge 6. An alloy as claimed in claimS having apermeability length of 1" and a gauge diameter of 0.25". Duplicate not greater than about 1.2. tensile tests were conducted at room temperature, 75 F., Heat treatment hardened austenitifi Steel articles and at an elevated temperature of 1000 F. on blanks having a maximum permeability of about 1.2 and good from each heat. The tensile properties and hardness P y Properties at both room temperature and elevatvalues obtained are set f rt-hi Tabl V111 ed temperatures consisting essentially ofcarbon from 7 Table VIII 7 Test. 0.02% 0.2% Ultimate Elonga- Reduc- Heat Temp. Yield Yield. Strength tion tion of Hard- Number F.) Strength Strength (p.s.i.) (Percent) Area ness (p.s.i.) (p.s.i.) (Percent) It is apparent from Tables VII- and VIIT that an iron about 0.35 to about 0.60%, manganese from about 8.0 base carbon-chromium-manganese-nickel-vanadium alloy to about 12.0%, silicon up to about 1.0% max., chromium in which the elements are within the narrow critical from 6.0 to about 10.0%, nickel from 4.0 to about 8.0%, ranges which I have specified has highly desirable and vanadium from about 1.1.t0v about 1.8%, sulphur up to unexpected tensile properties and hardness at both room about .03% max., phosphorus up to about .05 max, temperature and elevated temperatures. 7 and the balance substantially all iron and incidental im- My invention may be embodied within the scope of purities, said steel articles being age-hardened by solution PPfsannealing, followed by aging at temperatures'betweerr I claim: 900 F. and 1600 F.

1. An austenitic ironbase alloy consisting. essentially of 8. Heat treatment hardened austenitic non-magnetic carbon from about 0.35 to about 0.60%, manganese from ir'on base alloy steel articles having good physical propabout 8.0 to about 12;0%, silicon up to about 1.0% max., erties at both room temperature and elevated temperachrornium from about 6.0 to about 10.0%, nickel from tures consisting essentially of carbon from 0.-35 to about about 4.0 to about 8.0%., vanadium from about 1.1 to 0.60%, manganese fromabout-SzO to about-120%,- siliconabout 1.8%, sulphur up to about 03% max., phosphorus up to about 1.0% max, chromium from about 6.0 to up to about .05'% max, and the balance substantially all about 10.0%, nickel from about 4.0 to about.8.0%, vana-' iron and incidental impurities, said alloy being characterdium from about 1.1 to about 1.8%, sulphur up to about ized by good physical properties at both room tempera- 0.03% maX., phosphorus up to about 0.05%, and the balture and elevated temperatures, low magnetic permeabilance substantially all iron and incidental impurities, said ity, good hot and cold working characteristics and good steel being age-hardened by solution annealing at temage-hardena'bility. peratures in the range from about 2000" F. to 2200 F.,

2. An alloy as claimed in claim 1 having a maximum 5 cooled and then age -hardened at temperatures between permeability ofabout 1.2. 900 F. and 1600 F.

3. An austenitic iron base alloy consisting essentially R f r n e Ci i h file' of hi p t of carbon from about 0.45 to about 0.60%, manganese ED AT PATENTS from about 8.0 to about 10.0%, silicon up to about 1.0% y max., chromium fro'm.6.75' to about 8.25%, nickel from g 1957 ger et a1. Dec. 23, 1958 about 7.0 to 8.0%, vanadium from about 1.35 to about 3 062 692 M p anganello et a1. Nov. 6, 1962 1.65%, sulphur up toabout .03% max., phosphorus up to about .05 max., and the balance substantially all iron FOREIGN PATENTS and incidental impurities, said alloy being characterized 741,053 Great Britain. Nov. 23, 1955 by good physical properties at both room temperature and 562,401 Canada Aug. 26, 1958 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,163,526 December 29, 1964 Norman R. Harpster It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Columns Sand 6, Table IV, under the heading "Ultimate Strength, p.s.1.", line 1 thereof, for "24,500" read 124,500

Signed and sealed this 4th day of May 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Aitcsting Officer Commissioner of Patents 

1. AN AUSTENITIC IRON BASE ALLOY CONSISTING ESSENTIALLY OF CARBON FROM ABOUT 0.35 TO ABOUT 0.60%, MANGANESE FROM ABOUT 8.0 TO ABOUT 12.0%, SILICON UP TO ABOUT 1.0% MAX., CHROMIUM FROM ABOUT 6.0 TO ABOUT 10.0*, NICKEL FROM ABOUT 4.0 TO ABOUT 8.0%, VANADIUM FROM ABOUT 1.1 TO ABOUT 1.8%, SULFUR UP TO ABOUT .03% MAX., PHOSPHORUS UP TO ABOUT .05% MAX., AND THE BALANCE SUBSTANTIALLY ALL IRON AND INCIDENTAL IMPURITIES, SAID ALLOY BEING CHARACTERIZED BY GOOD PHYSICAL PROPERTIES AT BOTH ROOM TEMPERATURE AND ELEVATED TEMPERATURES, LOW MAGNETIC PERMEABILITY, GOOD HOT AND COLD WORKING CHARACTERISTICS AND GOO AGE-HARDENABILITY. 